2-propylheptanol and its esters

ABSTRACT

Diesters of 2-n-propyl-n-heptanol with dicarboxylic acids, e.g. phthalic, sebacic, azelaic and adipic acids, are used as plasticizers for vinyl resins.  An example is given of the use of di(2-n-propyl-n-heptyl)-phthalate as a plasticizer for a vinyl chloride copolymer, containing over 95% of vinyl chloride, in comparison with other di-decyl phthalates and di-(2-ethyl-hexyl) phthalate.ALSO:The invention comprises diesters of 2-n-propyl-n-heptanol will dicarboxylic acids, e.g. phthalic, sebacic, azelaic and adipic acids.  The esters may be prepared by mixing the alcohol with the acid or its anhydride, preferably with heating and in the presence of an esterification catalyst.  The 2-n-propyl-n-heptanol may be prepared by subjecting n-valeraldehyde to an aldol condensation and dehydrating the aldol to 2-n-propyl-2-n-heptenal in a single stage and their catalytically hydrogenating the heptenal either in 2 stages to give successively 2-n-propyl-n-heptenal and 2-n-propyl-n-heptanol or in a single stage to give 2-n-propyl-n-heptanol directly.  The 2-n-propyl-2-n-heptanol may be produced by adding a solution of n-valeraldehyde to a hot solution of an alkaline catalyst, e.g. sodium or potassium hydroxide or an alkali metal cyanide.  In the example 2-n-propyl-n-heptanol, prepared as above, is heated with phthalic anhydride in the presence of sulphuric acid as catalyst to give the diphthalic ester.

United States PatentO 2,921,089 Z-PROPYLHEPTANOL AND rrs ESTERS 3 Claims. (Cl. 260-475) This invention relates to a new alcohol and esters with dicarboxylic acids.

Our novel alcohol is 2-propyl-heptanol,

to its We have prepared this alcohol by subjecting n-valeral- I dehyde to al-dol condensation, with dehydration of the resulting aldol to 2-propyl-2-heptenal, followed by hydrogenation in two stages, to give successively 2-propyl heptanal and 2-propyl-heptanol, or in a single stage to give 2-propyl-heptanol directly.

The dehydrated aldol product of n-valeraldehyde,

namely 2-propyl-2-heptenal, is produced by feeding a solution of n-valeraldehyde to a hot solution of an alkaline catalyst. Although theconcentnation of alkali used is not critical, it is preferred to use 210% sodium or potassium hydroxide solution. Alkali cyanides may also be used as catalysts. The ratio by volume of Water layer to organic layer in the aldol reactor can vary within wide limits. As much as 95% water layer to 5% organic layer may be used, or as little as water layer to 70% organic layer. Reaction temperatures varying from 50 C. to 150 C. have been used; we have found that optimum results are usually obtained in the temperature range of 90-110 C. or at the boiling point of the caustic solution. By operating in the preferred temperature range and using strongly alkaline catalyst solutions, high yields of Z-propyl-Z-heptenal can be obtained. We have also found it advantageous to hold the salt concentration in the aldol reactor below 10% calculated as sodium valerate, and we prefer to operate at salt concentrations below 5%. Higher salt concentrations increase the solubility of the organic reactants in the water layer, and thus actually catalyze the formation of additional salts, thereby reducing the yield of the desired product.

Example 1Preparation of 2-propyl-2-heptenal.-Two hundred grams of 5% aqueous sodium hydroxide was brought to vigorous reflux. 810 g. of n-valeraldehyde was added dropwise, over a period of one hour, at reflux temperatures, with vigorous stirring. The organic layer was separated, and distilled from 2% sodium hydroxide solution. The product was dried on a Dean-Stark trap, and purified by distillation through a 30-pl-ate column at 4:1 reflux, to give 560 g. of 2-propyl-2-heptena1, boiling at 208-209 C. 2-propyl-2-heptenal azeotropes at 97.5 C. with 80% water. The organic layer contained 0.82% water, and the water layer contained 1.7% organic.

Example 2Preparation of 2-propyl-2-heptenal.- Eight thousand six hundred grams of n-valeraldehyde was fed to a small continuous aldol reaction system with a, l-liter holdup. An organic-to-water ratio of 70:30

was maintained; the water layer averaged 2% caustic and less than 5% salts calculated as sodium valerate. The n-valeraldchyde was fed through the system in approximately 8 hours, the reaction temperature being maintained at 93-97 C. The product overfiowed continuously through a decanter, and the organic layer was distilled from 2% caustic solution on a 30-plate column. A 97% yield of 2-propylheptenal azeotroping at 97.5" C. was obtained.

Example 3-Preparati0n of 2-pr0pyl heptemzl.Five hundred grams of 2-propyl-2-heptenal prepared in Example 2 was hydrogenated with 5% Raney nickel and 5% Water in an autoclave at C. until the unsaturation had been reduced to 6% calculated as 2-propyl-2-heptenal. The product was removed from the autoclave and decanted from the catalyst, washed with water, and filtered through Filter-Cel (a form of diatomaceous earth, sold by the Johns-Manville Sales Corp). The crude product was dried on a Dean-Stark trap and distilled on a 100-plate column. An 81% yield of 2-propyl-heptenal, boiling point 199 C., was obtained.

1 Example 4Preparati0n of 2-propyl-heptanoL-One liter of 2-propyl-2-heptenal prepared in Example 2 was hydrogenated with 5% Raney nickel and 5% water in a stainless steel autoclave at C. and 300 p.s.i. The hydrogenation was substantially complete in 2 hours with a residual carbonyl of less than 0.1% as 2-propyl-2-heptenal. The crude product was discharged from the autoclave, decanted from the catalyst, washed with water and filtered through Filter-Cel. The alcohol was dried and distilled on a 30-plate column at 5:1 reflux. A 96% yield of 2-propyl-heptanol, boiling at 215 C. at 760 mm., was obtained.

The di-esters of 2-propyl-heptanol with dicarboxylic acids containng only carbon, hydrogen and oxygen atoms have particularly valuable properties as plasticizers for vinyl resins and cellulose esters. In particular, they impart to these plastics, improved retention of flexibility at extremely low temperatures: a property which is of steadily increasing importance. They also have exceptional properties as synthetic lubricants. These esters may be prepared by conventional methods from 2-propyl heptanol and the appropriate acid or acid anhydride.

Example 5Preparati0n of di-(Z-propylheptyl) phthalate.-Four hundred grams of 2-propyl'heptan0l, 148 g. of phthalic anhydride, 0.05 ml. of sulfuric acid and 100 ml. of toluene were heated to reflux in a roundbottom flask equipped with a Dean-Stark trap. The theoretical quantity of water was removed rapidly. After the toluene and excess alcohol had been distilled off, the di-(Z-propylheptyl) phthalate remaining had an APHA color of 35. It distilled at 178 C. at a pressure of 0.15 mm. Hg.

Using the same and similar conventional esten'fication procedures, the following 2-propylheptano1 esters of dicarboxylic acids were prepared:

Ester Boiling Point Dl-(Z-propylheptyl) sebacate Dl-(Z-propylheptyl) azelate Dl-(2-propy1heptyl) adlpate 205210 C. at 0.07 mm. Hg. 192 C. at 0.25 mm. Hg. 178l82 C. at 0.25 mm. Hg.

is: r; Good-rich cheniic al 'co; The AS TM designations according to which the properties were tested are to be compositions which are to be used at very low tempera tures.

Properties of Geon 101 plasticized with various phtltalates Di-(2-iso- ASTM Di-(Z-pro- Di-(2-ethpropyl Mixed Commercial Property Designation pylheptyl) ylhexyl) .methyl- Di-Decyl Dl-Decyl Phthalate Phtlialate hexyl) Phthalates Phthalate j Y Phthalate Tensile strength, p.s.i D882-54T 2700 '3000 2800 2750 "2850 Elongation, pereent D882-554'I 360 330 i 350 375 340 Tean resistance D100449T 420 330 500 430 370 Durometer hardness". D314-521 90 84 96 '02 88 135 000 p.s.i. mod, C. Dl043-51 52 44 -44 Soapy water extraction (loss)... D1239- 0. 1 0.1 0.1 0. 1 Heptane extraction (loss) ,D1239-55 29 =22 '25 27 Y Activated carbon (loss) D120355 0. 3 1. 5 0.8 0.6 0.6 Retained elongation (oven test-1 week at 120 C.) D882-54T 84 49 0 78 73 l di-(2-prop ylhept yl) phthalate and 30% di-(2-propyl-4-metl1y1-hexyl) phthalate.

found in Part 6 of ASTM Standards, 1955, published by the American Society for Testing Materials. The plasticizers tested are di-(2-propylheptyl) phthalate, 'three other di-decyl phthalates, and, as a s'tandand plas'tici'zer, di-(Z-etliyl-heXyl) phthalate. I V

. ln the table, the'line 135,000 p.s.i. mod, C. shows the temperatures at which the apparent modulus of rigidity is 135,000 pounds per square inch. It will be noted that'for di-(2-propylheptyl) phthalate this temperature is 8 degrees lower than for di -(2-e thyl hexyl) phthalate or for commercial di-decyl phthalate, and 12 degrees lower than for di-(Z-isopropyl "S-riietlijilhe'Xyl) phthalate. It will also be noted that substitution of di-(2-propyl-4 methyl-hexyl) phthalate'jfor 30% of the di-(Z-propylheptyl) p'hthalate raises this temperature 2 C.' Hence it is clear that di-(Z-propylheptyl) fihtlialate is an extremely valuable plasticizer for polyvinyl chloride What We claim as our invention and desire to be secured by Letters Patent of the United States is:

1. The di-(2-propylheptyl) ester of a dicarboxylic acid selected from the group consisting of phthalic acid and adipic acid.

2. Di-(2'propylheptyl) phthalate.

3. Di-(2-propylhepty1) adipate.

30 References Cited in the file of this patent UNITED STATES PATENTS 1,993,737 I Graves et a1. Mar. 12,1935 2,014,310 Carruthers Sept. 10, 1935 35 2,780,643 Buchner Feb. 5, 1957 OTHER REFERENCES 'Pratt et al.: I. ArnfChem. Soc. 76, 55 1954). 

1. THE DI-(2-PROPYLHEPTYL) ESTER OF A DICARBOXYLIC ACID SELECTED FROM THE GROUP CONSISTING OF PHTHALIC ACID AND ADIPIC ACID. 